Water leaving reflectance retrievals from MODIS, VIIRS, and Landsat8 data acquired over coastal waters

Bo-Cai Gao and Rong-Rong Li, Naval Research Lab DC, Remote Sensing, Washington, DC, United States
In the late 1990s, we developed a hyperspectral atmospheric correction algorithm for retrieving water leaving reflectances over coastal waters from remotely sensed high spatial and spectral resolution data. The hyperspectral imaging data collected with the NASA JPL AVIRIS instrument on board an ER-2 aircraft from an altitude of 20 km was used to guide the algorithm development. Through the analyses of AVIRIS data, we observed that water leaving reflectances for narrow channels near 0.75 micron over coastal waters were not close to zero due to scattering by suspended sediments. Therefore, we concluded that the utility of a narrow channel near 0.75 micron for estimating aerosol information over bright coastal waters would be very limited. We developed a spectrum-matching technique using SWIR channels above 1 micron, where water leaving radiances are more closer to zero, to estimate aerosol models and optical depths.

In early 2000s, with funding support from the NASA SIMBIOS Project, we modified the ocean version of the hyperspectral atmospheric correction algorithm, and developed a MODIS version of multi-channel algorithm for remote sensing of water leaving reflectances over turbid coastal waters from a combination of MODIS land and ocean channels. A SWIR spectrum-matching technique using MODIS channels centered at 1.24, 1.64, and 2.13 micron was used to estimate aerosol models and optical depths. Later on, we developed a VIIRS version of coastal water atmospheric correction algorithm. The VIIRS channels centered at 1.24, 1.61, and 2.25 micron with proper modeling of atmospheric CO2 and CH4 absorption effects and a SWIR spectrum-matching technique were used for atmospheric corrections. More recently, we developed a Landsat8 version of atmospheric correction algorithm with proper consideration of different atmospheric gaseous absorption effects within the broader Landsat8 bands. We will present examples of retrieved water leaving reflectances over coastal waters from MODIS, VIIRS, and Landsat8 images.